Automatic print head shifting device

ABSTRACT

Automatic shifting mechanism is provided to shift a pin matrix type head normally positioned closely spaced from a printing plane during printing to a retracted position away from the printing plane during carriage return movement of a carriage supporting the printing head. Movement of the printing head from printing and retracted positions is controlled by carriage limit position.

0 United States Patent 11 1 11 1 3,817,365 Zimmermann [4 June 18, 1974[54] AUTOMATIC PRINT HEAD SHIFIING 3,145,822 8/1964 Wales, Jr, 197/1 RDEVICE 3,534,847 10/1970 Willcox 197/18 3,572,238 3/1971 Andersen 197/1R Inventor: e t imm e g, 3,596,746 8/1971 Murat 197/111 x Germany3,610,518 10/1971 Metschnabl 101/93 C 3,724,631 4/1973 Kaczeus 197/18 X[73] Asslgneegg sy 3,776,340 12/1973 Moser 197/1 R FOREIGN PATENTS 0RAPPLICATIONS [22] May 1973 1,221,649 7/1966 Germany 197/1 R [21] Appl.No.: 365,130

Primary ExaminerRobert E. Pulfrey [30] Foreign Application Priority DataAssistant ExammerE' Elckholt Aug. 9, 1972 Germany 2239117 ABSTRACT [52us. or. 197/1 R, 101/93 0 Automatip shifting mechanism is 9 19 to shifta [51] Int. Cl B4lj 9/20 P matrix yp hfiead bf P 1 1 [58] Field ofSearch 197/1 R, 18, 60, 66, 68; Spaced Pnmmg Plane Pflmmg to 3 F 101/93C 94; 178/25 tracted positron away from the prrntmg plane durmg carnagereturn movement of a carnage supporting the [56] References i d printinghead. Movement of the printing head from UNITED STATES PATENTS printingand retracted positions is controlled by car- 2,567,134 9/1951Stuivenberg 101/93 cx posmon' 3,135,195 6/1964 Potter 101/93 C 4 Claims,2 Drawing Figures PATENTEMW an M AUTOMATIC PRINT HEAD SHIFTING DEVICEThis invention relates to pin matrix printers; more particularly, itrelates to an automatically operable shifting device for controlling thespacing between a pin matrix print head and a printing plane, and,specifically, it relates to a shifting device operable to retract theprinting head mounted on a movable carriage to an inactive positionspaced from the printing plane incident to carriage return movement andto restore the print head to a printing position closely adjacent theprinting plane on return of the carriage to a beginning of lineposition.

Pin type print heads, because of the short stroke of the pins to effectprinting, require that the spacing of the print head from the printingplane be kept uniform to assure even density of print from character tocharacter. Previously, such print heads have been associated withdevices for controlling the spacing of the print head from the printingplane according to the thickness of the information bearing record. Thishas been accomplished by sensing devices, for example, by headsresiliently spring biased toward the printing plane or associatedrollers mounted on the printing head which ride against the record andcause the spring biased head to retract according to record thicknesssensed by the roller. Sensing devices of this type which bear againstthe paper interposed between print head and printing plane are apt,atthe high return speeds of the carriage supporting the print head, todamage the paper and/or an inked ribbon and otherwise render illegibleprinted information.

In accordance with this invention, the above problem is alleviated inthe provision of a print head shifting device operable to increase thespacing between print head and printing plane during return movement ofa carriage supporting the print head to avoid frictional contact betweenprint head and record. In one embodiment, the print head is associatedwith a spring biased lever acting normally to retract the print headfrom a normal print position closely adjacent the printing plane. Meansare provided to automatically urge said lever against its spring biasand to latch it when a carriage supporting the print head reaches abeginning of line position thereby to hold the print head in printposition. Further, means are provided to release the latch incident to acarriage return command issuing when the carriage has moved to aparticular print location or on receipt of a prearranged signalfollowing printing of selected information in a line.

Accordingly, an object of the invention is to provide an automaticsystem for varying the spacing between a pin matrix head and a printplane according to the direction of movement of a carriage supportingsaid print head.

Another object of the invention is in the provision of a system fornormally releasably holding a print head in printing position closelyadjacent a printing. plane during movement of a carriage supporting theprint head in a printing direction and for releasing said print head formovement away from said printing plane incident to and over the intervalof a carriage return movement to a beginning of line position.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing in which like referencenumerals designate like or corresponding parts throughout the figuresthereof and wherein;

FIG. I is an elevational view showing a carriage supported pin matrixprint head in a retracted position with the carriage moving in carriagereturn direction; and

FIG. 2 is an elevational view similar to FIG. 1 showing the print headin printing position closely adjacent a printing plane after movement ofthe carriage to a beginning of line position.

Referring now to the drawing wherein like reference numerals designatelike or corresponding parts throughout the several views, there is shownin FIG. 1 a carriage 3 which is supported for movement relative to aprinting plane 4 on a pair of parallel guide rails 5 parallel to theprinting plane 4. The carriage 3 pivotally supports a lever generallydesignated by reference numeral 6 as at 7 which has a rightwardlyextending arm 8 the end of which is coupled as by a pin 9 to the housingof a pin matrix print head generally designated by reference numeral 11.The lever 6 also has a downwardly extending arm 12 whose end is formedwith a latching recess 13 adapted to cooperate with a latching pin l4 onthe end of a horizontal latch member or bar 15. The other end of thelatch member 15 is pivotally mounted on the carriage as at 16 and aspring 17 connected to an anchor 18 on the print head and to latchmember 15 intermediate its ends normally tends to bias the latch member15 upwardly into engagement with the end of lever arm 12. The lever 6 isnormally urged clockwise by a torsion spring 19 wrapped about pivot 7and having an end coupled to lever arm 12 as at 21. Thus, as shown inFIG. 1, the lever 6, since its recess 13 is to the left of the latchingpin, is not latched by the latch member 15, and, through its arm 8,retracts the print head 11 away from the printing plane in the directionof arrow I a sufficient distance to allow free carriage return movementof the carriage and head by suitable conventional means without theprint head contacting a record positioned between the end of the printhead and the printing plane to receive printing.

As the carriage moves in the direction of arrow II or to the left asviewed in FIG. 1, an abutment or pin 22, secured to the lever arm 12 andextending upwardly from the plane of the drawing, will encounter a frameabutment 23 in its path defining a beginning of line or left marginposition with the result that the lever 6 will be movedcounterclockwise, cam the latch member counterclockwise, and be held bycooperative engagement of the latching pin 14 of the latch member andthe latching recess on the end of lever arm 12, as shown in FIG. 2. Thismovement of the lever 6 against the bias of its spring 19 will move theprint head 11 in the direc tion of arrow III (FIG. 2) to print positionclosely adjacent the printing plane as illustrated in FIG. 2. Printingof a line of characters by pins in the print head may be accomplishedwith the carriage moving in the direction of arrow IV under control ofsuitable motive or escapement mechanism. On some selected point in theline of print a carriage return command will occur and function torelease lever 6 from latch member 15 as by rocking. the latch membercounterclockwise about its pivot with the result that the parts willreassume their FIG. 1 position until again the carriage returns tobeginning of line position. In one embodiment, the carriage returncommand may be a signal pulse that may be applied to momentarilyenergize an electromagnet 25 located to attract the latch memberdirectly or through an armature (not shown) and rotate it to releaselever 6.

The objects of the present invention to regulate the distance betweenthe printing head and the printing counterbearing are achieved by meansof simple, readily produced components enabling the distance between theprinting head and the printing plane to be increased for the returnmotion of the carriage so that damage to the information carrier by theprint head cannot occur even when the return motion of the carriagetakes place at a high rate of speed.

The present invention is not limited to the embodiment described andshown in the drawing, modifications being possible within the scope ofthe idea behind the invention. For example, instead of the detent pin ofthe latch member 15, the latch member may be provided with a recess intowhich the lever arm 12 snaps. It is also possible to design the lever 6itself so as to perform the function of the pin 22 at the end of leverarm 12. Finally, the disengagement of the lever 6 from the latch member15 may also be triggered by purely mechanical means rather than by themagnet, for instance, in response to the carriage encountering the rightmargin setter usually present in such printing systems together with anappropriate design of the latch member 15.

The invention claimed is:

1. In a pin matrix printer having a printing plane, a pin matrix housingand a carriage supporting said housing mounted for movement relative tosaid printing plane in writing and carriage return directions,

means on said carriage for releasably holding said housing in printingposition close to said printing plane to permit pins supported thereinto print against a record located in front of said printing plane, saidmeans being operative on release to retract said housing away from saidprinting plane, other means responsive to a carriage return signal forreleasing said holding means,

and further means cooperating with said means on said carriage forrestoring said matrix housing to said printing position on return ofsaid carriage to an initial beginning of line position.

2. ln a pin matrix printer as recited in claim 1, said means on saidcarriage for releasably holding said matrix housing comprising levermeans pivoted on said carriage and connected to said housing, springmeans biasing said lever in a direction to retract said housing. andlatch means for holding said lever against movement by said springmeans.

3. In a pin matrix printer as recited in claim 2, said other meanscomprising a latch member, a spring biasing said latch member tolatching position, and means responsive to movement of said carriage toan end of line position to operate said latch member against its springbias to release said lever means.

4. In a printer as recited in claim 3, said further means including anabutment on said lever means, and a frame stop positioned to engage saidabutment when said carriage is returned to force said lever means tolatched position.

1. In a pin matrix printer having a printing plane, a pin matrix housingand a carriage supporting said housing mounted for movement relative tosaid printing plane in writing and carriage return directions, means onsaid carriage for releasably holding said housing in printing positionclose to said printing plane to permit pins supported therein to printagainst a record located in front of said printing plane, said meansbeing operative on release to retract said housing away from saidprinting plane, other means responsive to a carriage return signal forreleasing said holding means, and further means cooperating with saidmeans on said carriage for restoring said matrix housing to saidprinting position on return of said carriage to an initial beginning ofline position.
 2. In a pin matrix printer as recited in claim 1, saidmeans on said carriage for releasably holding said matrix housingcomprising lever means pivoted on said carriage and connected to saidhousing, spring means biasing said lever in a direction to retract saidhousing, and latch means for holding said lever against movement by saidspring means.
 3. In a pin matrix printer as recited in claim 2, saidother means comprising a latch member, a spring biasing said latchmember to latching position, and means responsive to movement of saidcarriage to an end of line position to operate said latch member againstits spring bias to release said lever means.
 4. In a printer as recitedin claim 3, said further means including an abutment on said levermeans, and a frame stop positioned to engage said abutment when saidcarriage is returned to force said lever means to latched position.